I'm just amused that Miley is so desperate to be seen as grown up and mature, and yet thinks that this sort of immature prank is fun and ~clever. No, Miley. It isn't.
Well, I think it's a sign of how, after an adolescence in the entertainment industry, she has absorbed all the worst of that culture - she exhibits the belief that she is, actually, the centre of the Known Universe, for not actually doing a lot, other than being famous. While a few child stars have escaped this type of thinking, it's obviously very difficult to avoid. I admit I resent the children a little less than those around them who taught them to be like this.
(My mother tells a story she heard about Shirley Temple, whose mother was very strict on not allowing her to "go Hollywood". Apparently, she was once walking through a store with her mother, at the very height of Shirley-mania, and saw a shelf full of lifesized Shirley Temple dolls. She gasped to her mother, "Those dolls look just like me!" to which her mother said, "Yes. What a strange coincidence!" and led her away quickly.)